Endocrine System

Question 1

Describe Cell Signaling

Answer 1

signaling cell sends a signal (usually a chemical)

target cell receives the signal and responds to it

Question 2

Describe two systems of Long Distance Signaling

Answer 2

1. Endocrine System: chemical messenger (hormone) transported by circulatory system
2. Nervous System: electrical signal travels along a neuron and chemical messenger (neurotransmitter) is released

Question 3

What are 4 types of cell signaling? Describe them

Answer 3

1. Direct cell signaling: 2 cells in direct contact communicate through gap junctions where chemical messenger goes from one to the other
   2a. Autocrine: chemical messenger leaves cell and binds to receptor on itself
   2b. Paracrine signaling: chemical messenger binds to receptor on nearby cell (no circ. system involved)
2. Endocrine signaling: signaling cell dumps hormone into cir. system (long or short distance) then binds to receptor on receiving cell
3. Neural signaling: electrical signal leads to release of neurotransmitter that binds to receptor on target cell

Question 4

Describe the 3 regulatory components of cell signaling

Answer 4

1. Sensor: detects levels of regulated variable -> sends signal to integrating center
2. Integrating center: evaluates input from sensor -> sends signal to effector
3. Effector: target tissue that responds to signal from integrating center

Question 5

What is a Set Point?

Answer 5

The value of the variable that the body is trying to maintain

Question 6

What is the difference between Positive and Negative Feedback Loops?

Answer 6

Positive: output of effector amplifies variable AWAY from the set point
Negative: output of effector brings variable BACK to the set point

Question 7

Explain what happens to the thermoregulatory set point during a fever

Answer 7

fever involves an increase in the body’s thermoregulatory set point -> person feels cold because body perceives a state of hypothermia -> fever breaks and set point returns back down so person sweats until body temp is lowered

Question 8

Describe a Direct Feedback Loop

Answer 8

stimulus -> endocrine gland -> target organ -> response

- no integrating center; quick

Question 9

Describe a First-order Feedback Loop

Answer 9

stimulus -> integrating center -> target organ -> response

- no endocrine glands

Question 10

Describe a Second-order Feedback Loop

Answer 10

stimulus -> sense organ -> integrating center -> endocrine gland -> target organ -> response
- 1 endocrine gland + integrating center

Question 11

Describe a Third-order Feedback Loop

Answer 11

stimulus -> sense organ -> integrating center -> endocrine gland 1 -> endocrine gland 2 -> target organ -> response
- 2 endocrine glands + integrating center

Question 12

Describe the Direct Feedback Loop of atrial natriuretic peptide (ANP)

Answer 12

Stimulus = increased blood pressure
Endocrine gland = heart (atrium) - secretes ANP
Target organ = blood vessels in kidneys
Response = lower blood pressure

Question 13

What is Hypoglycemia? What problem does it cause?

Answer 13

blood glucose too low

brain cannot function

Question 14

What is Hyperglycemia? What problem does it cause?

Answer 14

blood glucose too high

osmotic balance of blood disturbed

Question 15

What does Insulin do?

Answer 15

lower blood glucose levels

Question 16

What does Glucagon do?

Answer 16

raise blood glucose levels

Question 17

Where are Alpha and beta cells found? What do they do?

Answer 17

Islet of Langerhans (in pancreas)
Alpha cells release glucagon
Beta cells release insulin

Question 18

Why are Insulin and Glucagon considered an Antagonistic pairing?

Answer 18

they are hormones that have opposing effects

Question 19

Describe the Antagonistic regulation of blood glucose

Answer 19

increased plasma glucose -> beta cells of pancreas increase insulin secretion -> target tissues -> increase glucose uptake -> decrease plasma glucose
(simultaneously)
increased plasma glucose -> alpha cells decrease glucagon secretion -> target tissues -> decrease glucose release -> decrease plasma glucose

Question 20

What type of feedback loop are insulin and glucagon involved in?

Answer 20

Direct feedback loop

Question 21

What are 3 pathways that regulate insulin secretion?

Answer 21

1. Direct feedback loop: increase blood glucose -> pancreas secretes insulin
2. (2) Direct feedback loops: Glucose receptors in digestive tract release CCK -> pancreas secretes insulin
3. Second-order feedback loop: stretch receptors in digestive tract -> integrating center (Enteric Nervous System) -> pancreas secretes insulin

Question 22

Describe Type 1 Diabetes

Answer 22

juvenile onset

body does not produce enough insuliin

Question 23

Describe Type 2 Diabetes

Answer 23

adult onset

target cells do not fully respond to insulin

Question 24

Why does obesity increase the risk for Type 2 Diabetes?

Answer 24

adipocytes release a hormone (resistin) which likely down-regulates the insulin pathway

Question 25

Why does a defect in the insulin pathway vary from person to person?

Answer 25

because so many proteins are involved in insulin signal transduction

Question 26

Why is it difficult to define Hypoglycemia? What is the first sign of being Hypoglycemic?

Answer 26

there is a range of blood sugar levels that could result in a reaction
the first sign is becoming completely incoherent

Question 27

What is Hyperinsulinism? What are some metabolic diseases that can cause it?

Answer 27

Always being Hypoglycemic

• Autosomal mutations
• Beckwith-Wiedemann Syndrom (overgrowth disorder)
• Insulin reaction when too much insulin given to a diabetic

Question 28

How is hormone diversity in vertebrates characterized?

Answer 28

evolutionary changes in the way tissues respond to a hormone (rather than a change in the hormone molecules)

Question 29

Give 2 examples of hormones that have the same effect in different animals

Answer 29

1. human growth hormone: increase rate of growth in fish

2. estrogen (from pregnant mares): used in post-menopausal women

Question 30

Give an example of a hormone that has a different effect in different animals

Answer 30

Prolactin:

• stimulates milk production in mammals
• inhibits metamorphosis & promotes growth in amphibians
• regulates water balance in fish

Question 31

What is the key vehicle for the endocrine system? Give examples of why they are considered diverse organic chemical messengers?

Answer 31

Hormones

ex. proteins, glycoproteins, steroids, biogenic amines, small peptides

Question 32

What are many hormones produced and secreted by?

Answer 32

produced by hypothalamus

secreted by pituitary

Question 33

Where can Hormone Receptors be? Where can Hormone Signaling occur?

Answer 33

• on surface of target tissue, within cytosol, in target cell’s nucleus
• endocrine, paracrine, autocrine pathways

Question 34

Describe how Peptide Hormones are synthesized, stored, and secreted. Give some examples of peptide hormones

Answer 34

• synthesized on rough ER (often as larger preprohormones)
• stored in vesicle as prohormones (proteolytic enzymes in vesicle then cut the prohormone into active hormone)
• secreted by exocytosis
• ex. ANP, CCK, Prolactin

Question 35

Where is the Pituitary gland (hypophysis) located? What 2 parts is it derived from?

Answer 35

at base of brain, resides within sella turcica (saddle-shaped cavity)
from (1) oral ectoderm and (2) neural tissue

Question 36

Describe the derivation of the Neural part of the pituitary gland. What two names are used to describe this part?

Answer 36

evagination from the floor of the diencephalon

Neurohypophysis = Posterior Pituitary

Question 37

Describe the derivation of the Oral component of the pituitary gland. What two names are used to describe this part?

Answer 37

outpocketing of the ectoderm from the roof of the mouth

Adenohypophysis = Anterior Pituitary